Reles Type Co

ABB
Effective:

Instruction Leaflet

41-103H

May 1984

Supersedes I.L. 41-103G, Dated June 1976

Type CO Circuit Opening
Overcurrent Relay

( | ) Denotes change from superseded issue

2.0 CONSTRUCTION AND OPERATION
CONTENTS
This instruction leaflet applies to the following
types of circuit opening relays:
Type CO-2 Short Time Relay
Type CO-5 Long Time Relay
Type CO-6Definite Minimum Time Relay
Type CO-7 Moderately Inverse Time Relay
Type CO-8 Inverse Time Relay
Type CO-9 Very Inverse Time Relay
Type CO-11 Extremely Inverse Time Relay

! CAUTION
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely.
Inspect the contacts tosee that they are clean
and close properly, and operate the relay to
check the settings and electrical connections.

1.0 APPLICATION
These induction overcurrent relays are used to disconnect circuits or apparatus when the current in
them exceeds a given value. When no suitable station battery is available, the circuit opening type relay
in conjunction with ac series trip coil is used to tripthe
circuit breaker.

The type CO relays consist of an overcurrent unit
(CO), a de-ion contactor switch (CS), an operation
indicator (OI) and an indicating instantaneous trip
(IIT) when required.
2.1 ELECTROMAGNET
The electromagnets for the types CO-5, CO-6, CO-7,
CO-8 and CO-9 relays have a main tapped coil
located on the center leg of an “E” type laminated
structure that produces aflux which divides and
returns through the outer legs. A shading coil causes
the flux through the left leg to lag the main pole flux.
The out-of-phase fluxes thus produced in the air gap
cause a contact closing torque.
The electromagnets for the types CO-2 and CO-11
relays have a main coil consisting of a tapped primary winding and a secondary winding. Two identical
coils on the outer legsof the lamination structure are
connected to the main coil secondary in a manner so
that the combination of all the fluxes produced by the
electromagnet result in out-of-phase fluxes in the air
gap. The out-of phase air gap fluxes produced cause
a contact closing torque.
2.2 DE-ION CONTACTOR SWITCH (CS)
This switch is a small ac solenoid switch whose coil is
energized from a smalltransformer connected in the
main current circuit. A cylindrical plunger operates a
spring leaf arm with a silver contact surface on one
end and rigidly fixed to the frame at the other end.

All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If furtherinformation is
desired by purchaser regarding this particular installation, operation or maintenance of this equipment, the
local ABB Inc. representative should be contacted.
Printed in U.S.A.

41-41-103H

CO Circuit Opening Overcurrent Relay

The overcurrent unit contacts are in the contactor
switch coil circuit and when they close, the solenoid
plunger moves upward to open the de-ion contactswhich normally short circuit the trip coil. These contacts are able to transfer the heavy current due to a
short circuit and permit this current to energize the
breaker trip coil.
2.3 OPERATION INDICATOR (OI)
The operation indicator is a small clapper type
device. A magnetic armature is attracted to the magnetic core upon energization of the switch. When the
switch closed two fingers on thearmature deflect a
spring located on the front of the switch, which allows
the operation indicator target to drop.
The front spring, in addition to holding the target, provides restraint for the armature and thus controls the
pickup value of the switch.
2.4 INDICATING INSTANTANEOUS TRIP UNIT
(IIT)
The instantaneous trip unit s a small ac operated
clapper type device. A magnetic...